1. Field of the Invention
The present invention relates to the technical field of a self-excited power conversion circuit, and more particularly to a self-excited TRI-electrode AC switch (TRIAC) dimming circuit applied in a panel light. and a self-excited electronic transformer is provided for simplifying the driving circuit structure in the panel light to lower the product cost, so as to improve the product competitiveness.
2. Description of the Related Art
To create a comfortable, bright and stylish reading space or working space, panel lights with a simple and elegant shape are installed to an interior ceiling. To drive the operation of the panel light, a driving circuit is generally installed between a main circuit and a control circuit of the panel light for converting utility power to output a working voltage required by a load, and an insulation circuit installed between the panel lights and the load has a function of controlling the current of the output voltage.
With reference to FIG. 1 for a driving circuit 1 of a conventional panel light, the driving circuit is a non-insulation boost power converter, comprising an inductor (L), a diode (D), a capacitor (C), a switch 10, a detection resistor (RS) and a PWM controller 11, and the inductor connected in series with an anode of the diode is coupled to a drain of the switch 10, and the PWM controller 11 is coupled to a gate and a source of the switch 10 and the detection resistor, and a cathode of the diode is coupled to the capacitor and then electrically coupled to at least one LED 12. The inductor receives an input voltage (Vin), and the input voltage is used for storing power when the switch 10 is electrically conducted, and the stored power and the input voltage are filtered by the capacitor and transmitted to the LED 12 when the switch 10 is cut off, so that the boosting effect of the driving circuit is achieved through the simple and low-cost driving circuit 1, and the low-voltage circuit structure successfully drives the LED 12 to emit light. As to the non-isolation power converter, the precision of a constant current effect is very low, and thus having the issues of safety and electromagnetic compatibility (EMC) and failing to comply with the dimming requirements of the present panel lights.
On the other hand, the self-excited driving circuit of a conventional incandescent lamp or a conventional halogen lamp has an isolation circuit structure and do not have the aforementioned issues. Such self-excited driving circuit achieves the direct conversion effect by a half-bridge resonant circuit and has the advantages and features of quick start, non-flickering, universally applicable for power circuits of different powers, simple structure and low cost. Although the structure of the self-excited driving circuit is simple, it is lack of a constant power control mechanism, so that the output power will increase with the input voltage, and the lamp is unable to maintain a constant brightness, and the lamp has a fast ageing problem.
In view of the aforementioned problems of the conventional self-excited driving circuit applied in a panel light, it is a main subject of the present invention to provide a solution to the safety issue of the non-isolation converter, improve the scope of applicability of the lamp, and improving the output stability of a circuit power while maintaining the simple structure.